Power supplies are often required to deliver power to remote devices/systems at remote locations and such a need arises in particular in relation to fieldbus power supplies.
Such supplies are employed to deliver power, and sometimes additionally data etc., to remote-located field devices from a central control/power supply location. The remote devices can take the form of any required equipment such as sensors, actuators, control switches etc. which can be found at different locations within, for example a processing plant. All such devices require power, and often a communication, connectivity to the central control location and it is not uncommon for such field devices to be found in hazardous, for example potentially explosive, environments where the avoidance or quenching of sparks/arcs can prove important.
Fieldbus power supplies are currently widely known and generally comprise one or more power supply modules offering one or more channels for the delivery of power to a corresponding number of fieldbus channels. Within each module, the plurality of channels are often isolated and have there own dedicated Power Supply Unit (PSU) and conditioner circuitry in order to feed each respective fieldbus channel as required.
It is also widely recognized that some degree of fault tolerance is desirable so as to ensure continued operation of the remotely-located field devices should one, or perhaps more, of the power supply modules fail. For this purpose, it is known to build a level of redundancy into field bus power supplies.
In one known arrangement, each of the modules is mirrored by a redundant module, thereby forming a redundant pair. In normal operation of such arrangement, one of the modules in the pair supplies power to the required fieldbus channel. Should the module supplying the power fail, the previously redundant module in the pair can then be switched-in for operation in order to meet the channel's power supply requirements whilst the failed module is investigated for repair or replacement as appropriate.
In an alternative system, the two modules can be arranged to share the power requirement generally on a 50/50 basis for normal operation; but wherein each has the capability to take on 100% of the requirement should the other fail.
The use of back-up power supply systems is in any case widely known for seeking to maintain a variety of possible power requirements, whether or not within the fieldbus environment, and one such example is disclosed in US-A-2007/0162771. While the level of redundancy discussed above can be considered as that involving 2N devices (where N is the number of devices needed to fulfill the power supply requirements during normal operation); the level of redundancy within this document includes an N+1 architecture, again where N is the number of devices that can jointly meet the total power requirements during normal operation.
Known power supplies such as the field bus power supplies as discussed above can prove disadvantageous and limiting with regard to their general construction and nature of redundancy in view of the high level of duplication of circuitry, and circuitry elements, required and also due to the relatively high loading requirements that can lead to operational characteristics, such as heating, requiring potentially expensive and/or inefficient and/or space-consuming compensating features such as heat sync requirements etc.
A desire for greater efficiency and/or cost effectiveness and/or compact design considerations is therefore identified by the present invention.